Historically, research on genetic and environmental factors affecting reproduction and subsequent development of the offspring has been centered on the female. After a year-long assessment of the world literature, however, the need for an epidemiologic study of male-mediated reproductive outcomes was clear. Therefore we have obtained data from the European Longitudinal Study of Pregnancy and Childhood being conducted at Bristol, England ("ALSPAC"). In the ALSPAC study, more than 7,000 partners of women who delivered infants in Avon County, England during 1991-2 provided lifetime occupational and toxic exposure histories. The infants and their parents will be followed for seven years. We have coded occupational histories of both mothers and father, using the British Standard Occupational Codes, and categorized the self- reported exposures on the job and in the home. Four studies are in progress. First is the investigation of the association of paternal occupation and/or self-reported exposure with fetal growth. Dr. Farrow is doing the same study using maternal data. The concordance between father's and mother's report of his occupation is being examined in the third study. Finally, we have completed a study on radiation to the gonads for medical purposes; there was a suggestive but non-significant decrease in fetal growth.